如何从外部 Jar 自动装配实体？

Question

我是 spring 引导的新手，我花了几个小时试图弄清楚为什么当我将我的实体移动到另一个项目时我收到错误：“java.lang.TypeNotPresentException:输入 net.learn.spring.entity.Book 不存在”。我错过了什么？

这是我的项目结构：

这是我的实体项目结构：

实体项目POM：

<project xmlns="http://maven.apache.org/POM/4.0.0"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <groupId>net.mystest</groupId>
    <artifactId>CommonVO</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <name> </name>
    <properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <maven.compiler.source>1.8</maven.compiler.source>
        <maven.compiler.target>1.8</maven.compiler.target>
    </properties>
    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-data-jpa</artifactId>
            <version>2.2.7.RELEASE</version>
        </dependency>
        <!-- https://mvnrepository.com/artifact/com.fasterxml.jackson.core/jackson-annotations -->
        <dependency>
            <groupId>com.fasterxml.jackson.core</groupId>
            <artifactId>jackson-annotations</artifactId>
            <version>2.11.0</version>
        </dependency>
    </dependencies>
</project>

这是我的 StartApplication class:

package net.learn.spring;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.CommandLineRunner;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

import net.learn.spring.entity.Book;
import net.learn.spring.repository.Repository;

@SpringBootApplication
public class StartApplication implements CommandLineRunner{
    
    @Autowired
    private Repository repository;
    
    public static void main(String[] args) {
        SpringApplication spa = new SpringApplication(StartApplication.class);
        spa.run(args);
    }

    @Override
    public void run(String... args) throws Exception {

        repository.save(new Book("Las 1000 y una noches"));
        
    }

}
package net.learn.spring.repository;

import org.springframework.data.repository.CrudRepository;

import net.learn.spring.entity.Book;

public interface Repository extends CrudRepository<Book,Integer>{

}
package net.learn.spring.entity;

import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.Table;

@Entity
@Table(name = "ta_book")
public class Book {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;
    private String name;

    public Book() {
    }

    public Book(String name) {
        this.name = name;
    }

    public Long getId() {
        return id;
    }

    public void setId(Long id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    @Override
    public String toString() {
        StringBuilder builder = new StringBuilder();
        builder.append("Book [id=");
        builder.append(id);
        builder.append(", name=");
        builder.append(name);
        builder.append("]");
        return builder.toString();
    }

    
}

POM:

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.3.1.RELEASE</version>
        <relativePath /> <!-- lookup parent from repository -->
    </parent>
  <modelVersion>4.0.0</modelVersion>
  <groupId>com.learn</groupId>
  <artifactId>LearningSpringBoot</artifactId>
  <version>0.0.1-SNAPSHOT</version>
    <properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <maven.compiler.source>1.8</maven.compiler.source>
        <maven.compiler.target>1.8</maven.compiler.target>
    </properties>
    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-data-jpa</artifactId>
        </dependency>
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <scope>runtime</scope>
        </dependency>
        <dependency>
            <groupId>net.test</groupId>
            <artifactId>CommonVO</artifactId>
            <version>0.0.1-SNAPSHOT</version>
        </dependency>
    </dependencies>
    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
    </build>
</project>

控制台输出

Answer 1

你能post pom.xml CommonVO项目的文件吗？另外，我建议您像这样向 StartApplication 添加 EntityScan 注释： @EntityScan("net.learn.spring.entity.*")

用于标识应用程序启动时扫描实体的基础包。

Answer 2

您必须扫描包含实体 class 的包裹。

@Configuration
@ComponentScan("com.package.external.class")
class Config {
...
}

Answer 3

像下面这样更新您的主要 class：

...
@SpringBootApplication
@EntityScan(basePackages = "net.learn.spring.entity")
public class StartApplication implements CommandLineRunner {
...

@EntityScan 告诉 Spring 您将 @Entity 文件保存在哪里（持久性上下文将使用这些文件）。由于您的主要 class 和实体 class 位于不同的包中，Spring 默认找不到您的实体，需要您显示它们的位置。

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